The invention relates to antivibration devices designed to be inserted for supporting and shockabsorbing purposes between two rigid elements, the shock-absorbing bringing into play the driving of a liquid through a throttled passage, and the relative movements to be damped of the two rigid elements comprising on the one hand oscillations of relatively large amplitude (that is to say greater than a mm) at relatively low frequency (that is to say less than 20 Hz) and on the other hand vibrations of relatively small amplitude (that is to say less than 0.5 mm) and relatively high frequency (that is to say higher than 20 Hz).
By way of a non-limiting example, it is indicated that such supports can be mounted between a vehicle chassis and the motor of this vehicle, the relatively ample oscillations to be damped being those created by the irregularities and variations in declivity of the ground during the running of the vehicle over this ground and the vibrations to be damped being those due to the operation of the engine.
The invention relates more particularly, among supports of the type concerned, to those which are constituted by a fluid-tight box interposed between the two rigid elements, said box comprising two rigid parts which can respectively be made fast with the two rigid elements, a first elastic wall joining one of the rigid parts in fluid-tight manner to a rigid annular armature forming a portion of the second part, this wall defining with the first part one of the two axial ends of the box, a second elastic wall borne in fluid-tight manner by the annular armature and defining the second axial end of the box, a deformable partition also borne in fluid-tight manner by the annular armature, between the two elastic walls, and dividing the inside of the box into two chambers, these two chambers communicating with each other through the above throttled passage, means for limiting to a small amplitude, that is to say less than 1 mm, the deflections of thepartition in the axial direction perpendicular to its middle plane, and a liquid mass filling one of the two chambers and at least the portion, of the other chamber, contiguous with the deformable partition.
With such a support, vibration of high frequency and of low amplitude exerted between the two rigid elements generates corresponding relative movements of the two rigid parts, which are transmitted to the deformable partition through the liquid and are manifested by a rapid succession of alternate deflections of this partition perpendicularly to itself, of amplitude less than the maximum possible value : the dimensions of the partition are in fact sufficient for the liquid then not to be driven through the throttled passage in opposite directions in synchronism with said vibration.
On the other hand, for oscillations of higher amplitude and of lower frequency, the amplitude of the corresponding deflections of the partition reaches its maximum possible value and the liquid is then driven through the throttled passage, which ensures the desired hydraulic damping by throttling this liquid.
Numerous arrangements have been proposed to constitute the deformable partition, the means limiting the deflection of this partition and the throttled passage.
It is an object of the invention to provide for this arrangement a system resulting in a particularly economic, robust and efficient construction.